It is old and well-known in the photographic art to reduce silver halide grains bearing a latent image with a dye-image-generating reducing agent, such as a color-developing agent, capable of providing a dye-image-generating reaction product. For example, color-developing agents react with silver halide grains bearing a latent image to form silver and oxidized color-developing agent. The oxidized color-developing agent can then react with a photographic color coupler to form a dye image. It is conventional practice to remove the silver image by bleaching and to leave the dye image for final viewing.
It has been recognized in the art that the density of the dye image which can be produced with a given amount of silver halide and exposure can be increased through the use of a redox amplification procedure. In redox amplification processes, a portion of the dye image can be formed just as in conventional silver halide development, as described above. In addition, the silver image, which in conventional color processing is a by-product of development of the dye image, is employed as an immobile catalyst to achieve the imagewise reaction of dye-image-generating reducing agent and an oxidizing agent, wherein the dye-image-generating reducing agent and the oxidizing agent are chosen so as to be substantially inert to oxidation-reduction reaction in the absence of the catalyst. The result is that a second reaction path is opened for the imagewise generation of a dye. As a practical matter, most or even all of the final dye image can be attributable to the redox reaction rather than development-generated dye. In redox amplification processing to form dye images, it is possible to employ such low silver contents that bleaching of the silver image can be readily dispensed with.
Cobalt(III) complex and peroxide oxidizing agents have been employed separately in redox amplification reactions. Although some catalysts, such as silver, are useful for redox amplification reactions employing either oxidizing agent, the catalyst requirements of the oxidizing agents are not coextensive and can be widely divergent. Accordingly, redox amplification processes employing peroxide oxidizing agents or, more succinctly, peroxide redox amplification processes have been treated in the art separately from redox amplification processes employing cobalt(III) complex oxidizing agents. For example, Matejec, U.S. Pat. No. 3,764,490 issued July 4, 1972, teaches the forming of a photographic silver image which can then be used to catalyze the redox reaction of a peroxide oxidizing agent and a color-developing agent. Useful catalytic materials are not limited to photographic silver images, but include noble metals of Groups Ib and VIII of the periodic table generally. Weyde et al, U.S. Pat. No. 3,684,511 issued Aug. 15, 1972, teach imagewise-exposing an iodoform or derivative compound to form a catalyst image for peroxide redox amplification.
British Pat. No. 1,329,444 published Sept. 5, 1973, teaches forming negative images through peroxide redox amplification. A peroxide redox amplification catalyst is formed by imagewise-exposing a simple or complex salt of a heavy metal of Group VIb, VIIb or VIII of the periodic table with a mono- or polybasic carboxylic acid. The formation of cobalt, iron and manganese complex catalyst images are specifically disclosed. British Pat. No. 1,341,719 is directed to an improvement of the above-noted process, wherein it is taught to stabilize photographic elements containing dye images produced by certain specified peroxide redox amplification reactions so that it is unnecessary to wash out the reaction products while at the same time avoiding dye fogging on storage. Stabilization is said to be achieved through the use of polyvalent metal ions of metals of Groups Ib, IIb, IIIb, IVb, Vb, VIb, VIIb and VIII of the periodic table.
While gelatin is known to contain as impurities metals of a type which are known catalysts for peroxide redox amplification reactions, such as manganese, I am unaware of any teaching in the art to make use of these impurities in forming dye images through redox amplification reactions.
The use of cobalt(III) complexes in bleach-fix solutions is generally well-known in the art. British Pat. No. 777,635, for example, teaches the simultaneous bleaching and fixing of a subtractive color negative using a cobalt aquo-ammine cationic complex and a silver halide solvent as the bleaching and fixing agents. Stephen, U.S. Pat. No. 3,615,508 issued Oct. 26, 1971, teaches bleaching and fixing with a cobalt(III) ammine or amine complex, a thiosulfate fixing agent and a salt of an ammine or amine cation having an ionizable proton.
Bissonette, U.S. Ser. No. 402,432 filed Oct. 1, 1973, commonly assigned, now U.S. Pat. No. 3,923,511, issued Oct. 12, 1975, teaches concurrently bleaching and forming a redox amplification dye image in a monobath containing a cobalt(III) complex functioning both as an oxidizing agent and a bleaching agent. Bissonette, U.S. Ser. No. 602,156 filed Aug. 6, 1975, commonly assigned, now abandoned and refiled Oct. 12, 1976, as U.S. Ser. No. 731,284, teaches bleaching a silver image in a photographic element using a cobalt(III) complex to form an immobile cobalt image pattern which can be used as a catalyst for a peroxide redox amplification reaction. Bissonette, U.S. Ser. No. 609,880 filed Sept. 2, 1975, commonly assigned, now abandoned and refiled Oct. 8, 1976, as U.S. Ser. No. 730,914, teaches the combination of peroxide and cobalt(III) complex redox amplification in a single process wherein an immobile cobalt reaction product formed by cobalt redox amplification serves as a catalyst for peroxide redox amplification.
It is known in the art that cobalt(III) complexes can be exposed to light to form images. For example, Hickman et al, U.S. Pat. No. 1,897,843 issued Feb. 14, 1933, teach mixing thioacetamide with hexammino cobaltic chloride to form a light-sensitive complex capable of interacting with lead acetate to produce a lead sulfide image. Hickman et al, U.S. Pat. No. 1,962,307 issued June 12, 1934, teach mixing hexammine cobaltic chloride and citric acid to form a light-sensitive complex capable of bleaching a lead sulfide image. Weyde, U.S. Pat. No. 2,084,420 issued June 22, 1937, teaches producing a latent image by exposing Co(NH.sub.3).sub.2 -- (NO.sub.2).sub.4 NH.sub.4 to light or an electrical current. A visible image can be formed by subsequent development with ammonium sulfide. U.S. Ser. No. 618,186 by Adin et al filed Sept. 30, 1975, commonly assigned, discloses that images can be produced by employing a cobalt(III) complex in combination with a photoreductant. U.S. Ser. No. 610,954 by Do Minh filed Sept. 8, 1975, commonly assigned, now abandoned and refiled Oct. 30, 1975, as U.S. Ser. No. 627,393 discloses imaging with cobalt(III) complexes where a compound is employed in combination which promotes an internal gain. U.S. Ser. No. 629,931 by Brault et al filed Nov. 7, 1975, commonly assigned, discloses imaging using cobalt(III) complexes in combination with spectral-sensitizing dyes. Generally cumulative disclosures also appear in Research Disclosure, Volume 126, Item 12617, published Oct., 1974; Volume 130, Item 13023, published Feb., 1975; and Volume 135, Item 13505, published July, 1975.
The formation of reversal dye images in photographic elements is generally old and well-known in the photographic arts. In a typical approach, a silver halide photographic element capable of forming a multicolor image is imagewise-exposed and developed in a black-and-white photographic developer composition. The undeveloped silver halide is next rendered developable by uniform exposure or by fogging. The undeveloped silver halide is then developed using a color-developing agent so that a positive dye image is formed. Reversal processing has proven quite attractive, since it offers a convenient approach for obtaining a positive dye image using a negative-working silver halide emulsion without the necessity of first producing a negative dye image and then re-exposing a second photographic element through the negative dye image. Reversal processing to form positive dye images is widely employed in producing color photographic transparencies.
The teaching of forming reversal dye images in photographic elements using redox amplification processing is disclosed by Bissonette, U.S. Pat. No. 3,862,842 issued Jan. 28, 1975, in connection with cobalt(III) complex oxidizing agents. In one approach, it is necessary to bleach and fix image silver generated during black-and-white development in order to avoid uniform dye generation and, in a second approach, more fully described by Bissonette, U.S. Ser. No. 606,999 filed Aug. 22, 1975, commonly assigned, it is necessary to release a silver poisoning agent to get imagewise formation of dye. Both of these processes then introduce additional complexities in manipulative processing or element structure onto conventional silver halide reversal processing.
The formation of positive or reversal dye images in connection with peroxide redox amplification is also known in the art. In U.S. Pat. No. 3,694,207 by Matejec et al issued Sept. 26, 1972, positive dye images are formed by providing a uniform coating of a peroxide redox catalyst on a photographic support. Upon imagewise exposure, the redox catalyst is destroyed in light-struck areas. In U.S. Pat. No. 3,776,730 by Matejec et al issued Dec. 4, 1973, a positive dye image is formed in a peroxide redox amplification process by imagewise-exposing a silver halide photographic element containing a negative-working emulsion. The emulsion is developed using a black-and-white developer to form a negative silver image. Upon treatment with peroxide, the peroxide is quickly decomposed in the areas containing the silver image, thereby leaving behind a peroxide distribution in the unexposed areas of the photographic element. By incorporating in the photographic element substances which will decompose the peroxide at a slower rate than the silver image, such as sulfides, selenides, hydroxides, hydrated oxides or oxides of manganese, among other listed materials, the residual peroxide in the unexposed areas can be slowly decomposed under conditions which promote the formation of a positive dye image.